1. Field of the Invention
This invention relates to deformable mirrors for use as wavefront phase modulators in optical systems employing lasers which generate high energy flux levels. Such systems commonly utilize deformable mirrors to reflect a laser beam in a desired direction and/or to correct the laser beam for wavefront distortions, or to encode rhe laser beam by introducing known signals into the laser signal's wavefronts. Present day methods make it difficult to construct such a mirror so that it will reflect the totality of laser radiation incident on the mirror's reflecting surface. As a consequence, due to the flux level of the incident laser beam, the small portion of laser radiation that is absorbed can cause thermal overloading of the mirror's reflecting surface and its supporting structure, resulting in unwanted random distortions being created across the mirror's reflecting surface. In severe instances, the thermal overload can cause physical damage to, or destruction of, the mirror surface and/or its supporting structure.
2. Description of the Prior Art
The use of a fluid for cooling mirrors used in laser applications to dissipate thermal loads imposed by the laser beam are known in the prior art. See, for example, U.S. Pat. Nos. 3,909,118; 4,143,946; 4,202,605; or 4,239,343.
The use of deformable mirrors for correcting aberrations in laser wavefronts or for adding known distortions to laser signals is also known. It is generally appreciated that precise control of the deformations introduced into a mirror's reflecting surface must be maintained to insure that all measurable deviations in a laser signal are removed or, if the mirror is being used to encode a laser signal, to insure that the encoded signal closely replicates the signal intended to be encoded. Selective local deformation of the mirror's reflecting surface may be achieved by the use of piezoelectric actuators which may be selectively energized by the application of electrical signals thereto to produce mechanical forces which may be applied to the rear surface of the mirror. Precise control of the distortions introduced into the mirror's reflecting surface may be achieved by spacing the actuators close to each other and by having the surface area of the mirror influenced by each actuator being kept as small as possible, and by making the structure which carries the reflecting surface as thin and flexible as feasible. However, it is also known that the structure carrying the mirror's reflecting surface can absorb an appreciable quantity of heat when laser signals of high flux density impinge thereon and/or when the laser is operated continuously.
The laser mirror disclosed in this application provides a coolant path which avoids pumping coolant through actuators located in the central area of the mirror's reflecting surface by disclosing an arrangement in which the coolant is transferred toward and away from elongated, coolant-carrying channels which traverse substantially the entire width of the reflecting surface through coolant-conducting members which are positioned around the periphery of the reflecting surface. This arrangement permits the actuators used to control deformations within the central region of the reflecting surface to be packed densely together, thereby permitting very precise control of small surface areas of the mirror's reflecting surface, without the difficulty associated with making fluid-impervious connections between closely-spaced actuators and the central region of a mirror's reflecting surface.